pre wash in piping hot water

Aside from prewashing (I wash and dry in the dryer twice), I heavily starch flannels before cutting. This stabilizes it so it doesn't stretch out of shape with handling.

The process I use is (1) mix a 1:1 solution of Sta-Flo liquid laundry starch and water, (2) apply to fabric with a large wall painting brush, (3) when fabric is saturated I toss it in the dryer, and (4) iron with steam. This leaves the flannel with the stiffness of light cardstock -- very stable for precise cutting and piecing.

It's a good idea to use 1/2-inch seams with flannel too.

Since your pieces are already cut out, you might want to make a rag quilt out of them instead of the usual pieced quilt.

Because of my time here on the board, I knew to prewash to shrink the flannel, so that shouldn't be a problem. I will have to try the starch. Rag quilts take a larger seam, too, so I guess I better get ready to cut more fabric whatever solution I use.

Thanks, everyone for all your input. :-)

And when you iron, don't use steam. That will stretch the flannel.

Ooooo. I did not know that steam stretches flannels. Thanks for the tip.

I always have to prewash flannel. Then it behaves for me.

Yes, I have actually had flannel that was prewashed "grow" back to it's original size when I steamed it. It can also happen while starching too.

I should add that it's okay to use steam if you pre-starch with my method -- which involves saturating the flannel with starch and tossing in the dryer first. With this method there is enough dried starch in the fabric that the steam simply activates the starch without stretching the flannel.

That is great to know...I will try it next time I use flannel. Thanks for the tip.

Well, here's the result. Thanks for your help, everyone.